Some signs or billboards are designed to be viewed both during the day and during the night. During the day the illumination for the sign is typically daylight reflecting off the front surface of the sign. At night the signs are illuminated with a light source. Some signs are illuminated with a light source that mimics daylight by directing light towards the front surface of the sign. Other signs are backlit with a light source that is behind the sign that directs light through the sign.
Backlit signs may have an image printed on the front side of the sign and a mirrored copy of the image printed on the back side of the sign. When viewed during the day the front image is seen. When viewed at night the final image seen is a combination of the image printed on the back side of the sign and the image printed on the front side of the sign. The image printed on the back side of the sign may be less saturated than the image printed on the front side. By printing a less saturated copy of the image on the back side the combined image seen at night can be color matched to the front side image when viewed during the day.